Sulfur Sorption Research Articles

Sorption of Sulfur in Highly Leached Humid Soils of North East India

ABSTRACT High rainfall areas suffer from severe leaching loss of sulfate owing to their negatively charged nature. Sorption of sulfur (S) onto soil particles protect it from leaching out of the system. The S-sorption characteristics in humid soils from north-eastern India was studied with the objective to identify factors controlling S-sorption behavior in these acidic soils. Soils were collected from six different locations of north-eastern India. The soils were equilibrated with increasing concentrations of S for the sorption study, and later equilibrated with 0.01 N CaCl2 for desorption study. Results were fitted to three different isotherm models (Freundlich, Langmuir and Tempkin). The data fitted well to all three isotherm models. However, Freundlich adsorption isotherm yielded the best fit. Sorption parameters like S-sorption maxima (k), bonding energy (b), adsorption capacity (K), bonding energy constant (A) were positively correlated with the clay and, crystalline iron (Fe) and aluminum (Al) content in soil. Supply parameter increased with the increasing concentration of sulfate, while equilibrium buffering capacity was found decreasing. Soils from Nongpoh and Mustem with higher clay and crystalline Fe and Al content exhibited higher S-sorption capacity, whereas those of Padu having lowest clay content reported least S-sorption. It is recommended that in a soil having low S-sorption capacity, the minimal amount of S should be applied at a time.

Sulfur Fractions, Distribution and Sorption Characteristics in Some Soils of Ogun State, Southwestern Nigeria

ABSTRACT Sulfur (S) fractions, distributions and sorption characteristics of some soils in Ogunstate, Southwestern Nigeria, were evaluated in ten different locations, the area lies with in the Derived Savannah and forest agro-ecological zone. Result showed available, adsorbed, organic and total S ranged from 3.9 to 19.8, 16.3 to 36.6, 214.9 to 412.9 and 248.8 to 446.6 mg kg−1 respectively. Organic S constituted 86.4 to 93.4% of total S. The mean status of available S was slightly above the critical limit of 10 mg kg−1. All fractions of S maintained significant positive correlation (p ≤ .05) with each other and total organic carbon, while available and adsorbed S had significant and negative correlation with soil pH, total nitrogen, available phosphorus and calcium. The S sorption behavior of the soils varied and increased with increase in S concentrations of equilibrium solution. The isotherm model for the ten locations was S-curved type. Sorption data were fitted to Langmuir and Freundlich sorption isotherms. Langmuir equation was best fitted to the S adsorption data in the ten locations except soils from Owode, Odeda and Ikenne. Langmuir and Freundlich parameters (sorption maxima, binding energy and maximum buffering capacity affinity constant and slope) were significantly correlated with some soil properties.

The Impact of Operating Parameters on the Gas-Phase Sulfur Concentration after High Temperature Sulfur Sorption on a Supported Mo-Mn Sorbent

The impact of operating parameters on H2S capture from a syngas mixture by a Mo-promoted Mn-based high-temperature sorbent was investigated. The parameters investigated included temperature, space velocity, H2S concentration in the feed gas, and steam content. The H2S and SO2 concentrations in the gas after passing over a bed of the sorbent were analyzed and compared with thermodynamic calculations. The results confirmed that low temperature, low space velocity, low H2S concentration, and a dry feed were favorable for achieving a low residual concentration of sulfur compounds in the effluent gas. The sorbent was able to reduce the residual H2S concentration to below 1 ppm under all tested conditions. However, the unavoidable steam content in the gas phase had a significant adverse effect on sulfur removal from the gas. An empirical model, containing the three variables, i.e., temperature, space velocity, and H2S concentration in the feed, was developed and can be used to predict the effluent H2S residual concentration after treatment by the 15Mn8Mo sorbent.

Epitaxial Silver Films Morphology and Optical Properties Evolution over Two Years

Silver and gold are the most commonly used materials in optics and plasmonics. Silver has the lowest optical losses in the visible and near-infrared wavelength range, but it faces a serious problem—degradation over time. It has been repeatedly reported that the optical properties of silver thin films rapidly degrade when exposed to the atmosphere. This phenomenon was described by various mechanisms: rapid silver oxidation, sorption of sulfur or oxygen, formation of silver compounds with chlorine, sulfur, and oxygen. In this work, we systematically studied single-crystalline silver films from 25 to 70 nm thicknesses for almost two years. The surface morphology, crystalline structure and optical characteristics of the silver films were measured using spectroscopic ellipsometry, ultra-high-resolution scanning electron microscopy, and stylus profilometry under standard laboratory conditions. After 19 months, bulk structures appeared on the surface of thin films. These structures are associated with relaxation of internal stresses combined with dewetting. Single-crystalline silver films deposited using the single-crystalline continuous ultra-smooth, low-loss, low-cost (SCULL) technology with a thickness of 35–50 nm demonstrated the best stability in terms of degradation. We have shown that the number of defects (grain boundaries and joints of terraces) is one of the key factors that influence the degradation intensity of silver films.

Peculiarities of sulfur dioxide sorption from air by weak base anion exchangers

Peculiarities of sulfur dioxide sorption from air by weak base anion exchangers

Results of Research into the Content of Rare Earth Materials in Man-Made Phosphogypsum Deposits

According to the materials of the Rivne exploration expedition in Rivne region more than 15.3 million tons of phosphogypsum materials in rock dumps are stored. For further use and recycling of waste, it is necessary to evaluate the content of rare earth elements in phosphogypsum, which are of considerable economic value. The possible recycling of this production will increase the level of environmental safety through the use of more reliable engineering systems for the environmentally safe storage of phosphogypsum rock dumps. The migration of phosphorus, fluorine, sulfur, copper, chromium, manganese, zinc, lead, cadmium, iron, nickel and cobalt along the profile of the artificial ground cross-section was investigated experimentally. The results of studies confirmed the increased accumulation of metal in the phosphogypsum rock dumps. Analyzing the content of nickel, lead, sulfur, manganese, cobalt and zinc in experimental samples, we observe the distribution pattern, the content of which in samples is 2 – 3 times higher than the content of trace elements of the above-mentioned groundwater deposits. The results of the sorption and desorption of nickel, lead, sulfur, manganese, cobalt and zinc indicate that the rock is not an obstacle to the migration of trace elements and its aggregates in the rock and is observed only in the zone of full water saturation due to the filling of pore space. The conducted researches established the presence of phosphogypsum in man-made wastes of nickel, lead, cobalt, zinc, iron with a percentage content up to 1% per ton of rock waste.

Disproportionation of an Element in a Zeolite. III. Crystal Structure of a High-Temperature Sulfur Sorption Complex of Zeolite LTA Containing Two New Ions: Perthiosulfite, S42–, and the Trisulfur Cation, S32+

The structure of a high-temperature sulfur sorption complex of zeolite Na-A (LTA) has been determined by single-crystal crystallography. It was prepared by treating anhydrous Na-A with sulfur vapor at 623 K. Its crystal structure was refined in the space group Pm3m (a = 12.192(1) A) to the error index R1 = 0.075. Upon sorption, sulfur disproportionated fully to give one perthiosulfite anion, S42–, and one trisulfur cation, S32+, per unit cell. The perthiosulfite anion (S–S = 2.16(5) A and S–S–S = 105.4(22)°) is the perthio form of SO32–. It is in the large cavity where it bonds to one 6-ring and three 8-ring Na+ ions (S–Na = 2.83(6) A, 2.80(5) A, and 2.43(5) A). It appears to be the first example of a branched polysulfide ion. The electron-deficient trisulfur cation, S32+ (S–S = 2.11(8) A and S–S–S = 102.0(14)°), bonds to framework oxygen atoms in the sodalite cavity (S–O = 2.64(7) A). Twelve Na+ ions are found per unit cell at five crystallographic sites similar to but different from those in anhydrous ...

Influence of surface morphology on the performance of nanostructured ZnO-loaded ceramic honeycomb for syngas desulfurization

A facile seeding-growth protocol was employed to immobilize nanostructured ZnO with nanorod and nanosheet morphologies (ZnO-nR and ZnO-nS, respectively) on cordierite-mullite honeycomb support. By varying the hexamethylenetetramine (HMTA) concentration, Zn precursor, and number of growth cycles during synthesis, different nanorod sizes, nanosheets textures and ZnO layers were obtained. The ZnO-loaded honeycombs were characterized using FESEM, EDX and XRD indicating that the immobilized layer of nanostructured ZnO was highly-crystalline with a thickness of ∼1µm. The synthesized nanostructured ZnO-loaded honeycombs and a commercial ZnO sorbent were applied for removal of sulfur compounds (H2S and COS) from syngas at 400°C. The ZnO-nS showed significantly longer breakthrough time (BTTS) and higher total sulfur sorption capacity (48.7mgg−1 ZnO, BTTS=75.4min) than the ZnO-nR (9–12mgg−1 ZnO, BTTS=23–25min) and commercial ZnO sorbent (4.6mgg−1 ZnO, BTTS=6.8min). The superior sorption capacity of ZnO-nS was attributed to the significantly better surface coverage and higher crystallinity of ZnO nanosheets on the honeycomb. The introduction of additional ZnO nanosheets layers (up to 3 layers) through repeated growth process increased the ZnO loading to ∼1.5±0.1mgmm−1 (from ∼0.9±0.1mgmm−1 in the single layer) but resulted in poorer performance (11.6mgg−1 ZnO, BTTS=24.6min) compared to ZnO-nS. This was due to the increased internal mass transfer resistance and decreased density of the effective reactive sites. The mechanism of ZnO-nS formation is also proposed to provide further insights. Overall, the ZnO-nS showed better regenerability, lower mass transfer resistance, and higher sorption capacity compared to the commercial ZnO and ZnO-nR sorbents indicating that it has a promising potential for syngas desulfurization.

Effect of Cu-Doped ZnO Sorbents for Desulfurization

The purpose of this work is to synthesize undoped and Cu-doped ZnO sorbents by citrate-gel method and compare desulfurization efficiency, particularly H2S, at 150°C and 300°C. The undoped ZnO result shows a single phase of hexagonal zincite while the CuO monoclinic phase appeared with ZnO hexagonal phase in Cu-doped compositions (denoted by ZCx where x = mol% of Cu). The microstructure and surface area have been investigated by SEM and BET, respectively. The surface area decreases with the amount of Cu and all of them have a porous structure with small grains. The desulfurization performance of all specimens have been investigated by fixed-bed reactor. The results from breakthrough time indicate ZC20 sorbent has highest sulfur sorption capacity at 300°C. The XRD results show ZnO and CuO in ZC20 can absorb sulfur and completely transform to ZnS, cubic CuS and hexagonal CuS at 300°C.

Investigation of the influence of hollow aluminosilicate microspheres on properties of elastomer fire-thermal protective coatings

The paper considers the influence of the introduction of aluminosilicate microspheres on value of the Payne effect, rheometric, physico-mechanical thermophysical and fire-heat-shielding properties of the elastomer compositions used in the thermal protective coatings based on ethylene-propylene rubber. It was found that partial sorption of vulcanization accelerators and sulfur can occur on the surface of microspheres, followed by their desorption at the vulcanization temperature. This is confirmed by the appearance of a second peak on the vulcanization rate curve. The use of hollow aluminosilicate microspheres in the composition of elastomeric fire-heat-shielding coatings makes it possible to increase the efficiency of these compositions by reducing the thermal conductivity and density of the article while saving the optimum level of physico-mechanical properties. In accordance with the proposed mechanism for the interaction of the polymer matrix and microspheres, additional crosslinked structures are formed within the rubber matrix. An increase in the content of microspheres leads to an increase in the filler-filler interaction, which leads to a relative increase in thermal conductivity. However, the thermal conductivity of compositions containing relatively large amounts of the microspheres is still lower than that of the control. The introduction of microspheres slows down the heating of the sample during high-temperature tests, while reducing the loss of mass and the rate of linear combustion.

Improving the Efficiency of Coal-Gasification Combined-Cycle Power Plants by Using Natural Chemisorbent for High-Temperature Desulfurization of the Producer Gas

Test results on the selection and optimization of a natural sorbent for high-temperature desulfurization of gases produced by coal gasification at CCPPs are presented. The optimum sorbent-ferromanganese ore of the Askiz deposit-has a high sulfur sorption capacity and selectivity. Technical solutions for applying this sorbent at CCPPs of different capacity are developed and their efficiency is evaluated

Application of BaO-Based Sulfur Sorbent for in Situ Desulfurization of Biomass-Derived Syngas

A novel BaO-based sorbent is tested for in situ application as desulfurization agent in an allothermal biomass gasification process. BaO is stabilized against the formation of carbonate and thus theoretically allows desulfurization down to a few parts per million (volume) (ppmv) H2S even for high-steam and high-temperature conditions. In real process application, sintering of the sorbent occurred and had to be prevented by the addition of lime as separating agent. Additionally, a kinetic limitation of the desulfurization with BaO was shown for the in-bed sorption of sulfur. An increase of gasification temperature from 760 to 810 °C significantly improved the desulfurization performance. The observed behavior is in contrast to that of previously tested CaO-based in situ sorbents. CaO-based in situ desulfurization is limited to values of about 500 ppmv H2S for the conditions prevailing in the gasifier. With the novel BaO-based sorbent, a desulfurization from 85 to 35 ppmv residual H2S is shown upon addition...

Hybrid Polymer/UiO-66(Zr) and Polymer/NaY Fiber Sorbents for Mercaptan Removal from Natural Gas.

Zeolite NaY and metal organic frameworks MIL-53(Al) and UiO-66(Zr) are spun with cellulose acetate (CA) polymer to create hybrid porous composite fibers for the selective adsorption of sulfur odorant compounds from pipeline natural gas. Odorant removal is desirable to limit corrosion associated with sulfur oxide production, thereby increasing lifetime in gas turbines used for electricity generation. In line with these goals, the performance of the hybrid fibers is evaluated on the basis of sulfur sorption capacity and selectivity, as well as fiber stability and regenerability, compared to their polymer-free sorbent counterparts. The capacities of the powder sorbents are also measured using various desorption temperatures to evaluate the potential for lower temperature, energy, and cost-efficient system operation. Both NaY/CA and UiO-66(Zr)/CA hybrid fibers are prepared with high sorbent loadings, and both have high capacities and selectivities for t-butyl mercaptan (TBM) odorant sorption from a model natural gas (NG), while being stable to multiple regeneration cycles. The different advantages and disadvantages of both types of fibers relative are discussed, with both offering the potential advantages of low pressure drop, rapid heat and mass transfer, and low energy requirements over traditional sulfur removal technologies such as hydrodesulfurization (HDS) or adsorption in a pellet packed beds.

Regenerative Copper–Alumina H2S Sorbent for Hot Gas Cleaning through Chemical Swing Adsorption

This article focuses on desulfurization, of hot syngas from gasification of solid fossil fuels, in the temperature range of 300–500 °C via copper-based adsorbents. The slip of H2S above the developed adsorbent materials for hot cleaning of syngas has been studied together with the regeneration mechanism, using thermodynamic analysis, thermogravimetry, and packed-bed reactor experiments, in order to establish an efficient approach to regenerate the adsorbent. Supported copper on gamma alumina used as H2S adsorbent in this study shows H2S slips lower than 5 ppm in the temperature range of 350–550 °C. The copper-based sorbent shows around 2 wt % sulfur sorption capacity in the temperature range of study. The kinetic evaluation confirms that the sorption kinetics for this sorbent yield sufficient performance for real process operation even at such low temperatures. Aiming at isothermal operation, the chemical swing process is identified as an efficient way to regenerate the adsorbent. In this regeneration pro...

Effect of H2S in syngas on the Fischer–Tropsch synthesis performance of a precipitated iron catalyst

The sulfur limit, the relationship between the sulfur added and the surface Fe atoms lost (Fe/S), and mechanism of sulfur poisoning were studied using an iron Fischer–Tropsch synthesis (FTS) catalyst (100 Fe/5.1 Si/2.0Cu/3.0K). The FTS reaction was carried out at 230–270°C, 1.3MPa, H2/CO=0.67–0.77 and 30–70% CO conversion using a 1-L slurry phase reactor. The used Fe catalysts were characterized by XRD, Mössbauer spectroscopy and XANES spectroscopy to understand the deactivation mechanism of the Fe based catalyst after adding up to 1ppm H2S in the feed. Co-feeding of 0.1ppm H2S in syngas for 70h caused a very small change in the activity of the Fe catalyst, but increasing the H2S level to 0.2ppm or above resulted in measurable deactivation of the Fe catalyst over a similar time period. The limit of sulfur level in the syngas feed (sensitivity) was determined to be 50ppb. The added sulfur improved the selectivities of the secondary reactions of olefins and the WGS reaction even though the rates for these declined. The addition of H2S decreased CH4 selectivity and increased C5+ selectivities of the Fe catalyst. The Fe/S ratio, which can be used to define the poisoning ability of sulfur for the iron catalyst, was quantified based on the deactivation data obtained. The Fe/S ratio strongly depended on temperature and decreased remarkably with increasing temperature. At 270°C one sulfur atom was found to eliminate ∼6 surface Fe atoms, and the ratio increased to 7.2 at 260°C and increased further to 13.5 at 230°C. The Fe/S relationship with increasing temperature is in good agreement with sulfur sorption theory. The changes in FTS and WGS rates of the Fe catalyst by sulfur were also studied. The decreases in rates of the two reactions were nearly the same. The results of XRD and Mössbauer spectroscopy indicated that the online addition of sulfur did not greatly alter the distributions of iron carbide and magnetite. Both data sets consistently suggest an adsorption mechanism, in line with the results of reaction testing. XANES results at the S K-edge further confirmed sulfur adsorption, and some sulfide and sulfate species, likely confined to the surface zone, were detected. In this study, the sulfur tolerances of the precipitated Fe and a supported Co catalyst were compared at an identical temperature (i.e., 230°C), and similar M/S ratios (13.5–15.0) were obtained.

Low Temperature Desulfurization of H2S: High Sorption Capacities by Mesoporous Cobalt Oxide via Increased H2S Diffusion

Mesoporous cobalt oxides (M-Co-X, X = 150, 250, 350, 450 °C) with tunable porosity and crystallinity were synthesized based on an inverse micelle soft template method. They are the members of recently discovered University of Connecticut (UCT) mesoporous materials. The M-Co-X materials were investigated as desulfurizing sorbents in a fixed bed reactor in the temperature range of 25–250 °C. A considerably high sulfur sorption capacity was observed even at room temperature (13.4 g S/100 g sorbent), and very high values were observed in the temperature range of 175–250 °C (65.0–68.9 g S/100 g sorbent). The sulfided materials were further analyzed with LA-XRD, WA-XRD, N2 sorption studies, FESEM, FESEM-EDX, TEM, FETEM-EDX, TGA, and TPO. The M-Co-250 material reached 100% theoretical sulfur capacity at 150 °C. The presence of interconnected intraparticle voids and surface exposed particles were found to be the critical factors determining the ability of H2S to diffuse in the sorbent. The mesostruture of the M-Co-X material was preserved even after sulfidation. Other mesoporous metal oxides synthesized by the same method (Cr2O3 (UCT-37), CuO (UCT-11), Mn2O3 (UCT-1), and Fe2O3 (UCT-5)) also showed sulfur capacities of 2–200 times more than the corresponding nonporous materials.

황화수소 정제용 아연계 분무건조 탈황제의 활성성분 함량 변경에 따른 물성 및 반응 특성

Gaseous sulfur compound such as <TEX>$H_2S$</TEX> or COS in coal- or biomass-derived hot syngas can be purified by solid sorbents at high temperatures. In this study, we investigated the physical properties and reactivity of solid regenerable desulfurization sorbents with 37.2, 41.9, and 46.5wt% ZnO to look into the ZnO content effect. The sorbents were produced by spray-drying method to apply to a fluidized-bed process. Sulfidation and regeneration reaction were carried out using a thermogravimetric analyzer. Sorbent prepared with 46.5wt% ZnO had physical properties suitable for a fluidized-bed process applications such as spherical shape, sufficient mechanical strength and density, high porosity and surface area. It showed high sulfur sorption capacity of 10.4wt% (ZnO utilization of 57%) at reaction temperatures of 500 and <TEX>$650^{\circ}C$</TEX> for sulfidation and regeneration, respectively. However, the sulfur sorption capacity and ZnO utilization were significantly reduced and dimple shape appeared when the ZnO content decreased to 37.2 and 41.9wt%. Sulfur sorption capacity and regenerability were improved as reaction temperature increased within the experimental temperatures used in this work. The reaction temperature zones of <TEX>$1500{\sim}550^{\circ}C$</TEX> and <TEX>$650{\sim}700^{\circ}C$</TEX> are recommended for sulfidation and regeneration, respectively, to lead best reaction performances of the ZnO-based spray-dried sorbents developed in this work.

Microwave-Assisted Hydrothermal Synthesis of α-MnO2: Lattice Expansion via Rapid Temperature Ramping and Framework Substitution

Cobalt-doped cryptomelane-type manganese oxide (K-OMS-2) microwires have been successfully synthesized and characterized. Their catalytic activity was tested in an oxidation reaction with benzyl alcohol as the substrate, and the cobalt-doped OMS-2 materials showed 100% selectivity toward benzyl aldehyde with a conversion of 55%. The cobalt-doped OMS-2 materials were also investigated as a desulfurization sorbent in a fixed bed reactor at 250 °C where high sulfur sorption capacities (49.4 g of sulfur/100 g of sorbent) were observed. Here, structure-controlled synthesis was performed using a facile one-step microwave-assisted hydrothermal method (MWHY) associated with a rapid temperature ramping (200 °C/min). The structural effects induced by the compositional control of transition metal dopants on the cryptomelane (space group I4/m) body centered tetragonal structure were identified with X-ray diffraction (XRD) and transmission electron microscopy (TEM). The XRD and TEM results showed that the systematic v...

Sulfur removal from municipal gas using magnesium oxides and a magnesium oxide/silicon dioxide composite

Magnesium oxides (MgOs) were synthesized by polyol-meditation thermolysis, hydrothermal, and aerogel methods and utilized to remove sulfur compounds from municipal gas. The capacity to remove methyl mercaptan (291μmol/mol) from methane was evaluated by using an adsorption breakthrough method at different temperatures. Then, to improve the sulfur removal capacity, a MgO–SiO2 composite was developed using the aerogel method and its breakthrough capacity was compared to those of the MgOs. The synthesized MgOs and MgO–SiO2 composite were characterized by XRD, BET, TGA, and HR-TEM. The MgO prepared by the aerogel method had the highest surface area and sorption capacity among the as-synthesized MgOs. Furthermore, the sulfur sorption capacity of the MgO–SiO2 composite prepared by the same aerogel method as MgO was three times higher than the aerogel MgO even though the sorption capacity of SiO2 was negligible.

Sulfur Sorption under Maize–Wheat Cropping System as Influenced by Long-Term Effects of Chemical Fertilizers and Amendments in an Acidic Alfisol of Western Himalaya

Long-term effects of chemical fertilizers and amendments on sulfur (S) sorption under a maize–wheat system were investigated in a randomized block design with 11 treatments replicated three times, during winter (2007–2008) and summer (2008) seasons, in an ongoing long-term fertilizer experiment at the farm of College of Agriculture, CSK Himachal Pradesh Agricultural University, Palampur, India. Soils of the experimental site were acidic and classified taxonomically as Typic Hapludalfs. Soil samples taken from the surface (0–0.15m) after harvest of wheat (winter 2007–2008) and were analyzed for sorption behavior of S. Maximum sulfate adsorption was in 100% nitrogen (N)–phosphorus (P)–potassium (K) without S treatment and was attributed to continuous cropping without S application, leading to a deterioration of soil S fertility. Increases in the rate of long-term S fertilization caused a considerable reduction in the sulfate adsorption. Application of farmyard manure (FYM) as an amendment also reduced sulfate adsorption as compared to other inorganically fertilized plots. With the increase in the desorption of S in soil, the S concentration in soil solution increased.